Igneous rocks are those which solidified from a hot liquid which was either forced into older surrounding rocks (intrusive) or discharged on the earth’s surface as a lava flow or products from a volcano (extrusive).
The examples given below illustrate the two types. Everyone knows about the extrusive forms from accounts of present-day volcanoes and occasional lava flows, like those of Vesuvius, Paricutin, and Mauna Loa. An intrusion was injected beneath the Yellowstone Park area years ago, and its heat, with steam and gases, is contributing to the unusual natural features which are found in the park and which make it famous.
Igneous rocks in Missouri are:
[Porphyry], [Rhyolite], [Rhyolite porphyry]
Metamorphic rocks are rocks which have been changed through the effects of tremendous pressure (enough to raise mountains) and high temperature while in the solid state. In most cases a banded rock results. The metamorphic rocks mentioned in this booklet are: